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Thread: WR250R/X Airbox Mod

  1. #1
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    Default WR250R/X Airbox Mod

    In a previous thread, I mentioned that the Airbox Flap was put in for Noise Emissions for drive by testing. I've decided to remove it for less clutter and complexity. Some people are removing the airbox door.

    Here's how I removed the Airbox Flapper Solenoid and associated hardware;

    Here are the tools used and a picture of what will be removed;



    Screw Driver Flat Head
    Screw Driver Phillips Head
    5mm Allen Wrench
    1/4" Socket Wrench w/ 8mm and 10mm sockets
    1/2" Socket Wrench w 5mm allen attachment (not necessary but makes the radiator side cap screws easier to remove)
    You will also need a 1/8" rubber cap from an auto parts store.

    1. Remove all of the body panels. I removed seat, side covers, rear fender, both front air directors, unclip the ECU.



    2. Loosen the 3 screws that hold the gas tank on. Now you have access to the vacuum line under the tank. You can trace the vacuum line that goes to the throttle body because it attaches to the Black Plastic cylinder (the service manual says it's a Surge Tank). Pull the vacuum line from the throttle body and put a 1/8" rubber cap on the port. THE PORT NEEDS TO BE CAPPED.

    When pulling the rubber vacuum lines out, it's easier to detach the lines from the surge tank. I didn't bother trying to move the main wiring harness. It's not necessary if you just pull off the vacuum lines from the various parts.



    3. Next unscrew both the Surge Tank (black round thing) and the Intake Solenoid (behind the Surge Tank).

    4. Next remove the Solenoid that controls the Airbox Flap. You can do this by rotating the solenoid Counter Clockwise (if not try clockwise, I forget the exact direction). The solenoid will pop out. You will need to put a small screw driver down the airbox opening and pry the clip off. Here's what it looks like without the solenoid and associated hardware.

    5. To keep the Airbox flap in the down position, I drilled a small hole in the flap and the plastic directly below it. I used a 5/8" long self tapping screw to secure the flap (see picture).



    6. Here's a picture showing everything removed.



    The removal was a 45 minute job.

    A tip on removing the vacuum lines from the fittings is to use a flat head screw driver and pry between the vacuum line and part. If you try to pull it off, the rubber will cinch tighter around the fitting.

    Overall weight saved was not much, maybe 1.5lbs but there's much less complexity and clutter under the seat and to the bike in general.

  2. #2
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    Thanks for the directions. I thought the idea was to remove the door to get less restricted flow into the air box?
    R&F
    WR250X

  3. #3
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    Any negative effects or all just more power & HP
    Look ahead and haul ass
    13 CR450F 14 KTM XCW 07 TM 144
    PW 50 08 WR250X 08 KLX 110

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    Thanks Stom! I'm a big fan of simple too. Gonna gut it of everything I can.

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    Ride and Fly - The Airbox flap in the down position is open and not the other way around. You will be able to tell once you remove the seat.

    SkiCoach - In emailing Trail Zone magazine about why they removed the Airbox Hardware on their WR250R project bike, the response was that this Airbox Flap was used for Noise Emissions when doing Drive by Testing. I asked if there was any negative effects and they said no.

    Doing this mod is the same as removing the airbox door but you get rid of all of the clutter involved with the Airbox Solenoid. There is one electrical connection but it does not report to the ECU so it won't give you a CEL.

    In my quick spin around the block, everything performed as should.

    Albarelli - Your welcome. Let me know if you have any questions.

    My next thing will be removing the lines that went to the Charcoal Can. I've already removed the can but still have the lines. I've learned that the gas line is a vent that is required by CA. It's used to relieve pressure when pumping gas. Looking at the microfiche part numbers, the 49 state WRR/X has a different tank and gas cap. Most likely the 49 state cap vents. There's another line that runs off of the throttle body. I plan on capping this off. I'll let you know what happens.

    Side note the 49 state fuel tank is $289. The CA fuel tank is $1075! Also the fuel capacity in the CA model is lower.

  6. #6
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    Stom
    Thanks bro...
    Just ordered the K&N Filter and will do this mod when it comes
    Look ahead and haul ass
    13 CR450F 14 KTM XCW 07 TM 144
    PW 50 08 WR250X 08 KLX 110

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    Quote Originally Posted by stom_m3 View Post
    Ride and Fly - The Airbox flap in the down position is open and not the other way around. You will be able to tell once you remove the seat.
    Just looked at the picture and figured it out. Seal is on top of door (duh!)
    Thanks again.
    R&F
    WR250X

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    Removing 1.5 lb is a benefit in itself. I wonder how much total weight can be easily removed?
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    i already pulled all the lines for the charcoal can. i think my thread with pics is still here somewhere....

    i am going to do this mod when i put my power commander on this weekend.
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    did you cap the hose closest to the throttle body?
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    Quote Originally Posted by stom_m3 View Post
    Side note the 49 state fuel tank is $289. The CA fuel tank is $1075! Also the fuel capacity in the CA model is lower.
    Same deal for the DRZ. Different tanks/caps for CA models, and the caps/tanks are not interchangeable, as in, you cant use a CA tank w/ a 49 state cap and vice-versa. I wonder if the WR is the same way. $1075 for a fuel tank!

  12. #12
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    Quote Originally Posted by yamaha28 View Post
    did you cap the hose closest to the throttle body?
    The fitting on the throttle body needs to be capped. It's a vacuum line.

  13. #13
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    What did you cap it with.
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    You can pick up vacuum caps at your local auto parts store. They're cheap. It's just a rubber cap, presses right on.

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    I'm nervous about doing the K&N and the filter mod. I know the bike is FI but I still get nervous that the bike may get hard to start at some point or run badly at some rpm or maybe run a little to lean...can anyone make me feel better about it??? lol.
    If your not crashing, Your not riding!

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    Quote Originally Posted by KOCOMA View Post
    I'm nervous about doing the K&N and the filter mod. I know the bike is FI but I still get nervous that the bike may get hard to start at some point or run badly at some rpm or maybe run a little to lean...can anyone make me feel better about it??? lol.
    Do the mod and just monitor your spark plug on a regular basis, best way to tell if it is running lean or not. it will be apparent by a whitish color and/or bright white speckles.

    If it's a light brown color then you are good

  17. #17
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    Quote Originally Posted by garn View Post
    Do the mod and just monitor your spark plug on a regular basis, best way to tell if it is running lean or not. it will be apparent by a whitish color and/or bright white speckles.

    If it's a light brown color then you are good

    It's not the easiest task to get to that plug all the time. But I appreciate the answer. It's one that I knew in my head but these new 4 strokes put the plug so far in the motor it's crazy
    If your not crashing, Your not riding!

    2006 Vino 125(sticker charged)
    2008 WR250X

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    You can look at your spark plug t'il you're blue in the face and it'll tell you one thing: absolutely nothing. You can't read a plug w/ additive laden modern fuels in a 4-stroke. These ain't 2-strokes (unfortunately).

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    MPFab did some dyno work and stepped through several of the mods. His results (actually measuring AFR along with the dyno) was that the flapper mod plusheader and slip on exhaust got him into the upper 13's air-fuel ratio. Nothing to worry about there.

    After that he pulled the door off the airbox, it did run too lean (15+).

    Here's one of his posts over at TT (more stuff in that thread too):

    http://www.thumpertalk.com/forum/sho...45#post6615645

    So there's some actual measured data. The flapper mod plus some exhaust work does show some benefits and shouldn't be a problem, but if you open up the airbox further than just the flapper, then you may need to do something to add fuel.

  20. #20
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    Quote Originally Posted by stringburner View Post
    You can look at your spark plug t'il you're blue in the face and it'll tell you one thing: absolutely nothing. You can't read a plug w/ additive laden modern fuels in a 4-stroke. These ain't 2-strokes (unfortunately).
    Totally not true in my experience.

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    Good luck.

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    would it run to lean with the flapper mod and airbox door off?
    [SIGPIC][/SIGPIC]
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    Hey does anybody have the air box cover/pins/screw that they want to sell for say $10?

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    Quote Originally Posted by TreAdidas View Post
    Hey does anybody have the air box cover/pins/screw that they want to sell for say $10?
    Sure. PM sent.
    2011 Husaberg FS570
    2008 WR250X custom (clicky)

  25. #25
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    wow this really helped me out! thanks a million! I took the solanoid off today and rode around my neighborhood. Made a diff in power. felt a bit more sluggish on low end but top end got a boost. so did the noise level. my fmf pipe comes in tomorrow so that will be next. hopefully I get the bottom back although it wasnt much of a loss just maybe a bit of response. once again thanks

  26. #26
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    Warren, if I were you I would look into a fuel programmer before you run the pipe and the airbox mods. You may run it too lean without adding fuel to this equation.
    Ride.Race.Live. - 08 WR250X, 06 CRF250R, 03 YZ450F

  27. #27
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    FYI, there is also a quick and dirty method to increase the fuel by placing a 5k resistor in series with the air temperature sensor. This fools the ECU into thinking the air is colder than it really is, so the ECU will add more fuel to match the denser air. 5k will give you about +10% fuel across the board. Not the most graceful solution, but not that bad either. It will prevent you from running too lean if you're adding a new can and openning up the airbox.
    2011 Husaberg FS570
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  28. #28
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    Yup Dave, I put a 3.3k in and the intake temp reading dropped 30 something degrees F. Not sure exactly what amount of fuel that adds but helps IMHO.
    1998 XR200 *** 2002 RM250 *** 2008 WR250X tip it and rip it
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  29. #29
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    Then you could sell it on ebay as a "chip" that adds 10hp for $30, lol...

  30. #30
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    A 30 degree drop should get you around 6% more fuel. I got a 48 degree drop with a 5k, which should be about 10% more fuel (PV=nRT, T in Kelvin).

    MPFab did this first, and he mentions 5k - 7.5k would be about right for his setup with an aftermarket exhaust, custom header, K&N air filter and the airbox lid off.
    2011 Husaberg FS570
    2008 WR250X custom (clicky)

  31. #31
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    im thinking about doing this mod to mine...... but i really dont want to lose any bottom end, i could care less about top end. so im not sure its worth it me, since this bike set up for stunt.
    also any one do the clean air mod on their wr's?

    Quote Originally Posted by stom_m3 View Post
    My next thing will be removing the lines that went to the Charcoal Can. I've already removed the can but still have the lines. I've learned that the gas line is a vent that is required by CA. It's used to relieve pressure when pumping gas. Looking at the microfiche part numbers, the 49 state WRR/X has a different tank and gas cap. Most likely the 49 state cap vents. There's another line that runs off of the throttle body. I plan on capping this off. I'll let you know what happens.
    are there write ups for any of these other little mods

    Quote Originally Posted by rowdy View Post
    i already pulled all the lines for the charcoal can. i think my thread with pics is still here somewhere.....
    i didnt see your write up?
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  32. #32
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    Add the programmer...you'll see.

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    I did the flapper mod and felt almost nothing. Removed the AIS...nada. Then I added the FMF tuner. Played with it....found some settings online that seemed to help a tad and then I added an FMF powercore 4 which was underwhelming. If I had known $500 sooner that the bike would still be a turd I would have left it stock. I will admit that I gained 8-10 gps proven mph in top speed but I can barely feel it. I don't mind, I didn't buy the WR for its monster HP but I was hoping for a tad more. Oh well....its still a barrel of monkeys to ride.

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    Quote Originally Posted by QDRHRSE View Post
    I did the flapper mod and felt almost nothing. Removed the AIS...nada. Then I added the FMF tuner. Played with it....found some settings online that seemed to help a tad and then I added an FMF powercore 4 which was underwhelming. If I had known $500 sooner that the bike would still be a turd I would have left it stock. I will admit that I gained 8-10 gps proven mph in top speed but I can barely feel it. I don't mind, I didn't buy the WR for its monster HP but I was hoping for a tad more. Oh well....its still a barrel of monkeys to ride.
    For Me, when I changed the sprockets the bike finally felt "right" -1 tooth front +1 tooth rear. the speedo is wrong now and the top speed plummeted but thats ok!

    FMF pwrcore 4, AIS removed, flapper removed, stock filter, MPFab DIY servo sub, 3.3k resistor on air temp sensor (still no programmer), sprockets 12 - 43.
    1998 XR200 *** 2002 RM250 *** 2008 WR250X tip it and rip it
    You should be playing the RIDING GAME
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  35. #35
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    Quote Originally Posted by QDRHRSE View Post
    I did the flapper mod and felt almost nothing. Removed the AIS...nada. Then I added the FMF tuner. Played with it....found some settings online that seemed to help a tad and then I added an FMF powercore 4 which was underwhelming. If I had known $500 sooner that the bike would still be a turd I would have left it stock. I will admit that I gained 8-10 gps proven mph in top speed but I can barely feel it. I don't mind, I didn't buy the WR for its monster HP but I was hoping for a tad more. Oh well....its still a barrel of monkeys to ride.
    Thanks, that's what I wanted to know.

    Nice write up to the OP!
    Last edited by welding rod; 08-16-2010 at 10:20 PM.

  36. #36
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    I did this airbox mod, FMF Programmer, FMF Powercore, and Graves EXUP Module. I noticed quite a difference in throttle response, which is what I was after. It runs alot smoother to me too. Not alot more power but noticable.
    2008 Yamaha WR250X - Street
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  37. #37
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    Quote Originally Posted by Salty View Post
    I did this airbox mod, FMF Programmer, FMF Powercore, and Graves EXUP Module. I noticed quite a difference in throttle response, which is what I was after. It runs alot smoother to me too. Not alot more power but noticable.
    Did the jerkiness of the engine at slow speeds go away? Thats one thing that annoys me... in parking lots and stuff, the engine is real jerky... wish it was smoother on and off the throttle at slow speeds. I was hoping a few mods might smooth that out.
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    Yeah thats another thing I noticed it does smooth it out at low speeds. I hated that too. Downshifting is smoother as well. I think its worth it simply from improving the "ridability". No insane power improvement but I think its much nicer to ride now.
    2008 Yamaha WR250X - Street
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  39. #39
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    Quote Originally Posted by MotoBlogz View Post
    Did the jerkiness of the engine at slow speeds go away? Thats one thing that annoys me... in parking lots and stuff, the engine is real jerky... wish it was smoother on and off the throttle at slow speeds. I was hoping a few mods might smooth that out.
    Yes, the bike is smoother with all the mods for sure. The jerkiness, I think, is caused by the exup valve. When you add a slip on the valve is removed. My bike, although it doesn't feel faster, does have a lot more top end (per the GPS, not the butt dyno) and feels like its a little more snappy down low. Still, you could spend a lot and not be thrilled with the results. Make sure you like the bike a lot before you spend the money.

  40. #40
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    You're talking about top speed and that is more related to your gearing than anything. Yea if your bike has more power you can fight the air resistance a little better and go some what faster but I wouldn't say this is a good way of judging things. You could have been riding on a hotter day where the wind is less dense or on a road where the downhill is a little more inclined.

    I put a pipe on, opened up the airbox and tuned the FI and the bike felt new. Throttle response was significantly better, the entire power band felt smoother and much better, the bike at the track felt muuch more competitive... This bike ain't ever gonna compare to a race bike but with the mods it goes from being a simple street bike to a semi-track 250.
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  41. #41
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    I tested everything at the same time pretty much. I literally did something, came home, did something else. You're right to a point but if I'm making more power and I can only see/feel it at top speed, then its pretty obvious where I'm making all the extra power right? Its not where everybody is looking for it. I'm ok with the power that I have as I realize that its just a 250. I was just hoping for a little more hit down low. Most of the mods that everybody recommends are really only improving overall power on top and little down low or in the mid range. If gearing is the only way to get more bottom end then I'll try that too. I'm just saying....I sure wish that I could take the motor out of my WR450f and stick it in there.

  42. #42
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    NOTE: if you decide to remove the flapper (break it off) watch the sensor in the air box. Its a good idea to remove this sensor to prevent damaging it!
    1998 XR200 *** 2002 RM250 *** 2008 WR250X tip it and rip it
    You should be playing the RIDING GAME
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  43. #43
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    Just did the mod sounds a little more throaty with my Q4. Changed the plug while i was in there, figure what the hell it cant hurt.

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    My Powercore 4 definitely gave the bike a "thumper" sound. It sounds like a bigger bike. That I like very much.

    I just took my first long ride and boy was it rough. I went about 130 miles most of which was on the highway. I could not imaging making that ride on the WR250R. It was pretty uncomfortable on the X. The freeway I was on moves really fast and with my mods I was plenty fast enough to scoot down the highway, both uphill and downhill, @ 75-80 (true mph). The only problem I had was my MPG. I have no idea how much my bike holds in terms of fuel capacity but my low fuel light came on @ 60 miles or so. I rode home a little slower and after 70 miles the light is still not on. Overall, I still like the little WR but I'm definitely only going to ride it around the house. We have a couple of good local canyons to ride and I might try one of them out inthe near future. The one thing that really stood out is the way the bike glides around corners. It feels every bit as good as my old sport bike just without the monster power.

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